This talk explores a new path forward toward the goal of probing intermolecular and molecule-substrate interactions processes via tip-enhanced Raman spectroscopy (TERS). The combination of scanning tunneling microscopy and optical spectroscopy will be discussed as a promising approach to raise both the spatial and spectral resolution of molecules to an unprecedented level. I will focus in on three recent advances: 1. A new two-dimensional molecular superstructure of subphthalocyanine (SubPc) was discovered to consist of two distinct molecular binding configurations, both of which interact relatively weakly with the underlying metallic substrate as revealed by high-signal-to-noise enhanced Raman spectra. 2. We demonstrate the structural and chemical analysis of two porphodilactone regioisomers. Even though they are isomer, switching the lactone moiety would cause a significant change in their electronic structure. Following that, we have successfully distinguished these two regioisomeric molecules simultaneously through TERS with an angstrom scale (8 Å) spatial resolution. The molecule-molecule domain boundary was also characterized at a large scale using 2D mapping. 3. TERS spectra have been utilized to understand and confirm the distinct adsorption configurations on different substrates. We have identified porphodilactone molecules to form stable, long range 2D network on Ag(100) & Au(100), driven by attractive interaction, while on Cu(100), small and compact self-assemblies have been observed.

Probing intermolecular and molecule-substrate interactions at angstrom scale by ultrahigh vacuum tip-enhanced Raman spectroscopy

2019 Fall National Meeting

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